1. Field of the Invention
This invention relates to a self-sealing or unlined closure for a small container. More particularly, this invention relates to a self-sealing or unlined closure for a small, single use container of the type that has a thin and accurately formed closure engaging rim. Closures according to the present invention may be used to advantage with containers of the type known as culture tubes.
2. Description of the Prior Art
Self-sealing or unlined closures have been extensively used in the packaging of distilled spirits and various other comestible products. Such closures are normally applied to containers with fairly thick closure engaging rims, for example, glass containers which are formed by a blow molding process and plastic containers whose closure engaging finish portions are formed by blow molding or injection molding.
A self-sealing closure of the aforesaid type has a long thin flexible internal sealing fin which is adapted to engage a sealing surface on the top of the container finish, when the closure is applied to the finish, to form a suitable seal, even for a beverage container, without the need for a separate liner or lining material in the closure to effect the necessary seal. Examples of closures of this type are illustrated in U.S. Pat. No. 3,255,909 to Miller, et al., U.S. Pat. No. 4,069,937 to Smalley, and U.S. Pat. No. 4,360,114 to Owens.
Many packaging applications, however, utilize containers which are formed by the fabrication of glass tubing, and these containers, which include culture tubes that are widely used in scientific and laboratory applications, tend to have much thinner and more uniformly-formed walls and closure engaging rims than the blown containers that are used with closures according to the above-identified U.S. Patents. A thin-walled container, such as a culture tube, does not have sufficient width in its rim for proper sealing engagement with an internal sealing fin type of self-sealing closure, especially in the case of a small diameter culture tube, such as the 10 mm to 15 mm culture tubes which are especially popular for many laboratory and scientific applications. Additionally, thin-walled culture tubes are usually single use products, and need not be capable of being resealable. Thus, the resealability of the internal fin type of self-sealing closures, as described above, is not as important in a self-sealing closure for a culture tube as it is in the case of a closure for a liquor bottle, and certain economies may be realized in the production of closures for single use culture tubes by designs that would not meet the resealability requirements for liquor bottles and other multiple use containers.
Another type of self-sealing or linerless closure is depicted in U.S. Pat. No. 3,881,627 to Davolt. This closure utilizes an inner depending skirt which seals on a shoulder of a tooled inside surface portion of an associated plastic container, disclosed as being a vial. This closure has added complexity by virtue of the need for the inner sealing skirt, and can only be used with a special or non-standard vial, viz., one with the sealing shoulder to engage the inner sealing skirt of the closure and, apparently, this closure can only be used with plastic containers, possibly because manufacturing tolerances for glass containers are less precise, which could detract from the effectiveness of the inside surface seal provided by the inner sealing skirt of the closure.